Trigger_hurt can have different damage types.
I see 2 ways to do this.
#1
PHP Code:
if( attacker > 32 || is_valid_entity(attacker) || pev( attacker, pev_solid ) == SOLID_TRIGGER )
{
// trigger_hurt or ohter entity what did damage and have solid_trigger
// ps: only costom entities can be that way
}
#2
Ohter way is to find all trigger_hurts in plugin_init and set they for example pev_iuser to something and then check it.